Method of and apparatus for lining and impregnating a conduit



Aug. 1, 1956 c P. KUEBLER 2,759,864

METHOD OF ANJ APPARATUS FOR LINING AND IMPREGNATING A CONDUIT FJ' led Sept. 29, 1953 INVENTOR.

CARL P. KUEBLER ATTOR EYS United States Patent Ofiice METHOD OF AND APPARATUS FOR LINING AND IMPREGNATING A CONDUIT Carl P. Kuebler, Sidney, N. Y., assignor to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application September 29, 1953, Serial No. 382,993 13 Claims. (Cl. 154-228) This invention relates to flexible conduits or hose, such as those adapted for use in protecting and radio shielding an electrical conductor, or the like, and, more particularly, to methods and apparatus for making the same.

An object of the present invention is to provide a novel method of fabricating radio shielding conduits which are flexible and yet non-porous.

Another object of the invention is to provide a novel process for impregnating the porous walls of a flexible, metallic conduit for rendering the same non-porous without destroying the flexibility thereof.

A further object is to provide a novel method of making flexible, metallic tubing having the walls thereof impregnated with a solid, flexible compound whereby the manufacture of such tubing is simplified, and the cost thereof is substantially reduced.

The above and further objects and novel features of the present invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views:

Fig. 1 is an exploded side elevation view, with parts broken away and partly in section, showing one type of conduit which may be made by, and a portion of the apparatus which may be used in carrying out the method of the present invention;

Fig. 2 is an enlarged detail view, partly in section and with parts broken away, illustrating the internal construction of the conduit of Fig. 1, the section being taken substantially on line 2-2 of Fig. 1;

Fig. 3 is a partially exploded top plan view of novel apparatus used in practicing the method contemplated by the invention; and

Fig. 4 is a sectional view taken substantially on line 4-4 of Fig. 3.

In Figs. 1 and 2 of the drawing, there is shown, by way of example, one form of conduit 10 which may be fabricated in accordance with the novel method of the present invention. The specific form of the conduit illustrated comprises a plurality of superposed concentric tubes, or sleeves 14, 15, 16 and 17 each of which is a braided wire tube. The strands, when braided in a known manner to make up a tube, may be constituted in various forms known to the art, but in a preferred embodiment each strand is made up of about eight small wires laid side by side to simulate a flat strip. The tubes may be braided separately and inserted into one another, or the larger diameter tubes may be braided directly on the smaller ones, as a core. The smallest or inner tube is generally braided on a solid removable core, which has been removed from the illustrated conduit.

The ends of the multiple layer conduit 1417 have the end portions of the layers thereof firmly secured together by means of solder, and each said end is secured 2,759,864 Patented Aug. 21, 1956 by means, such as solder, within the channel of an annular ferrule 18.

The ferruled end of the tubing fits into a counter-bore or recess in an end fitting 12, and butts against an internal flange 20 therein. The inner diameter of flange 20 is preferably smaller than the inner diameter of ferrule 18 for a purpose to appear hereinafter. The outer circumference of the ferrule, and the inner closed end thereof are securely soldered to the wall of end fitting 12 in the recess provided therein. The outer end of ferrule 18 is preferably flush with the end of the end fitting, but if desired, the outer cylinder of the ferrule may be flared outwardly beyond the end of the fitting. The other end of the tubing is provided with a ferrule 18 in a similar manner, and is secured in an end fitting 11 against a shoulder 21 therein.

For the purpose of rendering the conduit moistureproof, and at the same time provide protection against the chafing of insulated wires passing therethrough, the above described conduit is treated in a novel manner to provide therein a lining 22, and at the same time provide thin layers 23, 24 and 25 of the lining material between adjacent layers of braided metal tubing. The lining material should be non-porous, flexible and resilient. Additionally, it should have good resistance to corona, and should not contain volatiles for some uses. When set, said material should retain these properties when subjected to a wide range of temperatures and exposed to grease, gasoline, and moisture. A suitable material should also be tough and have the ability to adhere to the braided metal tubing and withstand continual bending stresses. Elastomers, such as those having a poly vinylchloride base and silicone rubbers have been found suitable.

One lining material which has been found suitable for use in flexible conduits for radio shielding aircraft engine ignition systems, for example, is a synthetic plastic material known in the trade as a plastisol, i. e., a fluid dispersion of polyvinylchloride polymer in a plasticizer which may be converted by heat alone to an elastomeric vinyl compound. This material has a polyvinylchloride base with suitable plasticizers and a heat stabilizer. Suitable filler may be used, if necessary, to vary the flow characteristics. A suitable composition consists of ten parts, by weight, of polyvinylchloride, such as Geon #121, four parts of Rohm and Hass Paraplex G-SO (a polyester), two parts Paraplex 6-60 (a polyester) and two parts of a heat stabilizer consisting of a mixture of Paraplex 6-50 and dibasic lead phthalate in equal parts. This material is prepared for application at normal room temperature. The Geon #121 should be in the form of a fine powder, the plasticizers (Paraplex) are added in liquid form and the heat stabilizing mixture is added in finely powdered, well-mixed form. The ingredients are then mixed thoroughly, preferably under vacuum, and applied to the above described metal conduit structure in accordance with the novel method next described.

To effect impregnation and lining of the conduit with the plastisol described above or other similar compound in accordance with the novel method of the invention, the inner surface of braided tube 17 is preferably wetted with a suitable primer to promote adhesion between the lining and the metal tubing. One suitable metal primer for this purpose when the tubes are made of nickel, is commercially known as Unichrome #219 PX and may be applied with a swab. Care should be taken not to apply the primer to surfaces to which attachment of the coating or lining is not desired. If maximum flexibility is desired, the primer should not be permitted to permeate the mesh of the braided tubes. After the treated conduit has been thoroughly dried and cooled, the same is securely clamped in a close fitting resilient mold, leaving the ends of the conduit accessible. One form of mold which may be used in carrying out the method is illustrated in the drawing as comprising two halves 30, 30 which are hollowed out to receive the conduit and to preferably confine the latter under some pressure when the faces of the halves of the mold are pressed into firm engagement. The mold halves are made of resilient material, one suitable known material being a neoprene base compound known commercially as Scinflex. The mold material should preferably bev of about 65 to 70- durometer, but this is not critical and may vary somewhat.

When the conduit has been placed in the mold, the latter is put into, a suitable fixture for applying pressure to press the halvesof the mold together around the conduit. Such.a fixture may comprise a fixed side wall 31, and a movable side wall 32, between which the mold may be clamped, Ai-r, fluid, or mechanical pressure may be applied to the movable wall 32, toclamp and hold the mold under suitable compression between walls 31 and 32.

With the mold and conduit thus clamped, one end of the conduit is, connected to. a source of impregnating compound, above described through a supply pipe, or fixture, 33. The latter may fit intothe end of ferrule 12, and is preferably provided with a gasket 34 which engages, and is pressedifirmly against flange 20 to provide a seal. The compound which will. hereinafter sometimes be referred to as plastisol, is injected through pipe or fitting 33 into conduit 10 inthe form of a heavy, viscous, yet flowable material, a pressure of about 85 to 95 pounds per square inch being used. When the conduit is filled with plastisol as evidenced by the flow of the latter from the open end of the conduit, said open end is sealed by seating a plug 35 in ferrule 11 and applying axial pressure thereto. The injection of plastisol is continued under pressure of about 85 to 95 pounds per square inch until the compound begins to seep out through the crack between the adjacent engaging faces of the mold halves 30, 30. The resistance to such seepage, or flow, between the compressed halves of the mold is sufficient to insure that before it occurs the plastisol compound will have completely impregnated .the porous walls of the braided, metal conduit, thereby forming a non-porous wall structure completely free of air bubbles, voids, or the like. At the same time, no appreciable amount of the compound is permitted to collect on the surface of the conduit within themold.

The. conduit is then removed from the mold and suspended with the. longitudinal axis in a vertical positionto permitthe compound to drain freely. Draining should continue for from about ten minutes to an hour until the center hole is of suflicient diameter to receive an insulated conductor or the like of desired size. The impregnated conduit is then placed in an oven and baked at a temperature. of 350 to 400 F. for several minutes until the, plastisol has set to a weak gel. The conduits may now be cooled. and excess plastisol, if any, may be removed with astainless steel wire brush, care being taken not to flex the conduit, or injure the wire braid with the brush After thus cleaningthe partially cured conduit, the same is returned to the oven and baked at about the same temperature forfro-m 20 to 35 minutes, i. e., until the plastisol is thoroughly cured and set. The conduit is then cooled and is ready for. use.

There are. thus provided a reliable and effective method for fabricating. moisture-proof radio-shielding conduits andsimplifiedapparatus for use in practising said method. The. novel method and apparatus comprehended make it possible to fabricate. such conduits with assurance as to the highwqualityof .thefinished product and to effect such fabrication rapidly. and at low cost with a minimum Waste. of materials.

Although only a single embodiment of the invention has beenillustrated in the accompanying drawings and described in the foregoingspecification, it is to be expressly 4. understood that the invention is not limited thereto. For example, the method may be used to fabricate an infinite variety of conduits and the like which differ specifically from the one illustrated and the apparatus may be varied in shape to accommodate other forms of products. Various other changes may also be made, such as in the specific materials, temperatures and the like suggested herein by way of example and in the design and arrangement of parts illustrated without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

What is claimed is:

1. The method of lining and impregnating the porous walls of a conduit which comprises closely surrounding the porous walled portion of the conduit with a sectional mold of resilient material, pressing the mold sections against each other and against the external surface of the conduit, injecting a sluggish fluid compound into the conduit through one end thereof until the conduit is filled, sealing the other end of the conduit and continuing the injection of said compound until the latter seeps out between engaged faces of the mold sections, removing the conduit from the mold, suspcnding the conduit with its axis vertical to drain excess compound from the interior of said conduit, and halting the impregnated conduit to cure the compound retained therein.

2. The method of impregnating a conduit having porous walls which comprises clamping the conduit firmly in a sectional mold of resilient material, filling the conduit with a sluggishly fiowable compound, sealing one end of the conduit, providing a tight flow connection for such compound between the other end of said conduit and a source of such compound, and injecting additional compound into the conduit through said conncc.ion under pressure sufficient to force the compound through said porous walls and between the engaged surfaces of the mold sections.

3. The method of lining and impregnating the porous walls of a conduit, such as a braided metal conduit, which comprises placing a sectional mold of resilient material around said conduit intermediate the ends of the latter, applying external pressure to said mold sections to press the same into firm engagement with the external surface of said conduit and to press the adjacent faces of said mold sections together, filling said conduit from one end with a sluggishly flowing compound, sealing the other end of the conduit after the same is filled, injecting additional compound into the conduit under pressure until the compound permeates the porous walls of the conduit, removing the conduit from the mold, and draining excess compound from the interior of the conduit.

4. A method as defined in claim 3 wherein the compound is deaerated under vacuum prior to injecting the same into the conduit.

5. A method as defined in claim 3 comprising the further step of baking the impregnated conduit to reduce said compound to a non-flowable solid.

6.. A method as defined in claim 3 which includes the further steps of baking the treated conduit until the compound thereon is set to a Weak gel, cleaning excess compound from the surfaces of the conduit, and thereafter baking the cleaned conduit until the compound is fully cured.

7. The method of impregnating the porous walls of a conduit which includes tightly clamping the conduit in a sectional mold of resilient material, sealing one end of said conduit, providing a tight flow connection for a viscous compound between the other end of said conduit and a source of such compound, and injecting a flowable viscous compound into said conduit through said connection under pressure suflicient to force a fluid through said Walls and between the engaged faces of the sections of said mold.

8. A method as defined in claim 7 which includes the conduit before injecting the compound to promote adhesion between the compound and said surfaces.

9. The method of making a flexible conduit which includes the steps of assembling a plurality of braided wire tubes in telescoped relation to form a multi-ply metallic hose, clamping a sectional mold of resilient material around said conduit intermediate the ends of the latter, sealing one end of the conduit, providing a tight flow connection for a flowable compound between the other end of said conduit and a source of such compound, injecting a sluggishly flowable compound into said conduit through said connection under pressure until the compound permeates the spaces in the braided metallic walls of the conduit, removing the conduit from the mold, draining excess compound from the interior of the conduit, and baking the treated conduit until the compound therein is fully cured.

10. Apparatus for impregnating a conduit comprising a mold of resilient material for compressively surrounding a central portion of the conduit, means for clamping said mold around the conduit and for supporting the same in a fixed position, a compound supply line adapted to communicate with one end of said conduit in sealed relation therewith, means for closing the other end of said conduit, and means for supplying a flowable compound to said conduit under pressure through said supply line.

11. Apparatus as defined in claim 10 wherein said supply line is retractable and has gasket means at the end thereof for making sealing engagement with said conduit.

12. Apparatus as defined in claim 10 wherein the means for closing the other end of said conduit comprises a retractable plug.

13. Apparatus as defined in claim 10 wherein said mold comprises only two sections.

References Cited in the file of this patent UNITED STATES PATENTS 776,150 Smith Nov. 29, 1904 1,796,338 Moore Mar. 17, 1931 2,100,587 Chalker Nov. 30, 1937 2,111,639 Petersen Mar. 22, 1938 2,175,373 Baker Oct. 10, 1939 2,256,160 Britton et al. Sept. 16, 1941 2,289,734 Scott et al. July 14, 1942 2,463,231 Wyatt Mar. 1, 1949 2,544,430 McCutchan Mar. 6, 1951 FOREIGN PATENTS 634,056 Great Britain Mar. 15, 1950 

1. THE METHOD OF LINING AND IMPREGNATING THE POROUS WALLS OF A CONDUIT WHICH COMPRISES CLOSELY SURROUNDING THE POROUS WALLED PORTION OF THE CONDUIT WITH A SECTIONAL MOLD OF RESILIENT MATERIAL, PRESSING THE MOLD SECTIONS AGAINST EACH OTHER AND AGAINST THE EXTERNAL SURFACE OF THE CONDUIT, INJECTING A SLUGGISH FLUID COMPOUND INTO THE CONDUIT THROUGH ONE END THEREOF UNTIL THE CONDUIT IS FILLED SEALING THE OTHER END OF THE CONDUIT AND CONTINUING THE INJECTION TO SAID COMPOUND UNTIL THE LATTER SEEPS OUT BETWEEN ENGAGED FACES OF THE MOLD SECTIONS REMOVING THE CONDUIT FROM THE MOLD, SUSPENDING THE CONDUIT WITH ITS AXIS VERTICAL TO DRAIN EXCESS COMPOUND FROM THE INTERIOR OF SAID CONDUIT, AND BAKING THE IMPREGNATED CONDUIT TO CURE THE COMPOUND RETAINED THEREIN.
 10. APPARATUS FOR IMPREGNATING A CONDUIT COMPRISING A MOLD OF RESILIENT MATERIAL FOR COMPRESSIVELY SURROUNING A CENTRAL PORTION OF THE CONDUIT, MEANS FOR CLAMPING SAID MOLD AROUND THE CONDUIT AND FOR SUPPORTING THE SAME ON A FIXED POSITION, A COMPOUND SUPPLY LINE ADAPTED TO COMMUNICATE WITH ONE END OF SAID CONDUIT IN SEALED RELATION THEREWITH, MEANS FOR CLOSING THE OTHER END OF SAID CONDUIT, AND MEANS FOR SUPPLYING A FLOWABLE COMPOUND TO SAID CONDUIT UNDER PRESSURE THROUGH SAID SUPPLY LINE. 